Man holding up a sign that says World AIDS Day

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Yoxly Awesome Contributors

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Medically Reviewed by:

Dr Danae Maragouthakis

by: Christiana Funmi Ogunmodede

It's the 1st of December, and the advent chocolate calendars can finally come out. However, before we start munching away, let’s not forget today is also World AIDS day. Each year we come together to raise awareness about HIV, and this year is no different.

This year we discuss HIV pre-exposure prophylaxis (HIV PrEP), a firm cornerstone in England’s action plan to achieve an 80% reduction in new HIV cases by 2025 and zero new transmissions by 2030. Find out what PrEP is, how it came about, where to access it for free, how to take it and how effective it is.

What Is HIV PrEP?

PrEP stands for pre-exposure prophylaxis. It involves taking medication before unprotected sex to stop you from catching HIV. PrEP is not the same as HIV post-exposure prophylaxis (PEP), which is taken after sex to prevent HIV infection. For more information about PEP, see our previous article on it here. The two HIV medicines commonly used for PrEP are tenofovir disoproxil (TD or TDF) plus emtricitabine (FTC). 

What Is The History Behind PrEP?

The concept of HIV PrEP dates back to 1995 when scientists in the United States experimented with macaque monkeys. The monkeys were given an experimental HIV prevention drug and then exposed to simian immunodeficiency virus (a virus similar to HIV). The scientists found that the experimental drug prevented the monkeys from becoming infected with the simian virus. There were subsequent studies after this, and in 2007, the first large-scale HIV PrEP clinical trial (Iprex study) started. Three years later, the results were published, which showed a 44% reduction in HIV infections when the subjects took HIV PrEP. Other clinical trials took place in England in 2012 and 2017, which also demonstrated the effectiveness of PrEP. Eventually, in 2020, HIV PrEP became widely available in the UK for free to those deemed to be at high risk of getting HIV.

The illustration below summarises key events in the history of HIV PrEP. 


An infographic illustrating an overview of key significant event of HIV PrEP

How To Take PrEP?

There are two ways of taking HIV PrEP: daily dosing and event-based dosing.

Daily dosing: This involves taking ONE tablet every day. This is the recommended option for women taking PrEP and for transgender women on hormone treatment. The time to HIV protection is 7 days for vaginal sex.

Event-based dosing: Also known as the “on demand” dosing. PrEP is only taken when needed using the 2-1-1 dosing schedule. This means TWO tablets are taken 2–24 hours before having sex, one tablet 24 hours after sex and another tablet 48 hours after sex. This regime is only recommended for men who have sex with men only, as it has only been shown to be effective for anal sex.

How Effective Is HIV PrEP?

PrEP is very effective for HIV prevention. The Iprex study – the first HIV PrEP study in humans, showed that taking HIV PrEP reduces the incidence of HIV infection by 44%. The PROUD study showed that HIV PrEP reduces the risk of HIV infection by 86% in men that have sex with men. The Terrence Higgins Trust (The UK’s leading HIV and Sexual Health charity) also states that “HIV PrEP offers almost 100% protection against HIV.

Whilst PrEP is effective for HIV prevention; it does not protect against other sexually transmitted infections (STIs) such as syphilis, gonorrhoea and chlamydia. Therefore, it is highly recommended that individuals that use HIV PrEP have regular STI screening every 3 months.  You can stay on top of this using our affordable at-home testing kits.

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Where Do I Get PrEP From?

You can get free PrEP from your local NHS sexual health clinic if you meet the eligibility criteria. Alternatively, you can buy PrEP online if you do not qualify for free PrEP but still wish to use it.

In England, HIV PrEP is free if any of the criteria below applies:

  • You are HIV-negative with a HIV-positive partner, their HIV level is not yet undetectable, and you expect that you will have condomless sex with them (excluding oral sex)
  • You are a man or transgender women who has sex with men, you have had condomless sex (excluding oral sex) in the preceding 3 months, and you are likely to continue to do so in the next 3 months
  • When reviewed by specialist staff, you are assessed to be at high risk of acquiring HIV infection. This may include:
    • If you have condomless sex with partners from countries where HIV is more prevalent such as South-East Asia, Southern Africa
    • You are a commercial sex worker and have condomless (excluding oral) sex.

Before issuing PrEP, the clinic will ensure you meet one or more of the above criteria and perform some baseline blood tests (including HIV and kidney function). This is to ensure that you are not HIV-positive and have healthy kidney function before starting PrEP. You will also likely be offered a full STI screen (including syphilis, gonorrhoea and chlamydia. Then, you are issued three months' supply at a time, with repeat supplies issued as long as you still meet the eligibility criteria.

In Wales and Scotland, there may be additional eligibility criteria. Your local sexual health clinic will be able to advise you about this. I-base has a useful guide on safely buying PrEP online if you live in the UK. It is also important to mention that you can still get advice and support from your local NHS sexual health clinic even if you decide to buy HIV PrEP online. 

PrEP: The Present & The Future

It’s been 38 years since HIV was first identified, and a lot has changed. PrEP means we can prevent HIV in those at higher risk. HIV is also no longer a death sentence thanks to the multiple classes of HIV drugs available. The UK government continues to work hard towards reducing HIV transmission. They have met the UNAIDS 90-90-90 target for the last 3 years, i.e. 90% of those living with HIV are diagnosed, 90% of those with HIV are getting treatment, and 90% of people on treatment do not have HIV detectable in their blood.

Yoxly is proud of the achievements so far. We continue to do our part to raise awareness about HIV, and we also ask that you do the same, too. So hopefully, in 2030, we can look back and celebrate achieving the ambitious target of zero new HIV transmissions.


Christiana Funmi Ogunmodede is an Antimicrobial Pharmacist working for the Royal Berkshire NHS. In her role within the NHS, Christiana specialises in pharmaceutical administration for microbial diseases, infectious diseases, sexual health and HIV.


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Yoxly's Awesome Contributors (YACs) are a diverse group of individuals who are passionate about public health, and committed to furthering our mission. Yoxly provides a platform where a variety of sexual health topics (some more awkward than others!) can be explored, in an informative and non-judgmental way. If you'd like to become one of Yoxly's Awesome Contributors, contact us!